1. Field of the Invention
The present invention is directed to a two-way communication system which may find particular application as a complement to existing cable television communication systems.
2. Discussion of the Background
Cable television systems are conventional and well known, and a schematic diagram of a conventional cable television system is shown in FIG. 1. As is shown in FIG. 1, a conventional cable television system features a cable control station 5 which has a coaxial cable output therefrom. The coaxial cable carries television and control signals. Along the transmission path, amplifier stages 10(n) are utilized to amplify the transmitted signals to ensure that the signals transmitted along the coaxial cable are at an appropriate amplitude. Also, standby batteries 70 may be connected along the transmission path to provide back-up power in the event of a power failure. Connected to the amplifier stages 10(n) are various taps 15(n), and output of these taps 15(n) are the coaxial cables which are input to a user 20(n), e.g., the home of the customer. These taps 15 are typically formed on a utility pole, in an underground pedestal or, in a case of an apartment building, within a security closet.
Conventional cable systems suffer from several significant shortcomings and drawbacks.
One significant drawback is that the theft of the cable signals transmitted along the coaxial cable is very common. One type of cable theft is an unauthorized user simply accessing the cable tap 15, connecting an unauthorized cable thereto, and receiving the signals from the cable. Such a theft however typically does not allow the cable thief to access premium channels or pay-per-view channels. A further type of theft is if a user further has a decoder or descrambler to gain access to the scrambled premium or pay-per-view channels.
Cable systems have developed various techniques to combat such cable theft. To prevent unauthorized access of a tap, a locking terminator may be placed on the tap itself. One way of preventing viewers from receiving the premium or pay-per-view channels is that an extraneous signal, which may typically be 2.5 MHz, is inserted above a normal visual carrier. This causes the television at the user 20 to think it is receiving a strong signal, and the television then automatically adjusts for this gain, which results in overriding or hiding the real cable signal. To overcome these situations, a trap must be placed at the tap 15 to remove this extraneous signal, and this thereby allows any authorized channel to be viewed by the user 20.
Such a security system to ensure that users 20 only receive cable if they have paid for the service and receive the channels they pay for has a significant drawback in that any time a user 20 changes their service and either is entitled to receive additional channels or cancels certain channels, the cable system must dispatch a technician to the appropriate tap 15 to change the configuration of the traps therein. This is a costly and time consuming operation and a significant drawback in such a system.
Furthermore, any time a user 20 cancels a cable service, a technician must also physically go to the appropriate tap 15, which may typically be on a utility pole, disconnect the cable and, possibly place a physical lock on the tap 15. Such an operation is again costly and time consuming for the cable systems.
Another common situation of cable theft is the inadvertent theft of services. In such a situation, a cable user 20 inadvertently receives channels which the user 20 is not paying for and authorized to receive. This situation often occurs when a cable technician fails to disconnect the cable or install the appropriate traps in the taps 15 to block channels from reaching a user. Such a type of inadvertent cable theft is very difficult to detect in conventional cable systems as they can only be detected by a visual inspection of the taps 15.
A further problem in conventional cable systems is effectively addressing a cable-out situation in which for some reason cable signals are not properly transmitted to certain users. Such a cable-out situation may occur if a cable gets cut, if there is a power loss, etc. The conventional way of detecting such a cable-out situation is for a cable system to await complaints from the users, and then to send a technician to determine the cause of the cable-out.
A cable-out can be caused by a loss of electrical power. In such a situation, a user 20 that is experiencing a cable-out may not be experiencing a similar power loss in their home as their home may be served by a different utility transformer than the cable. It is common for a cable system to have standby batteries 70 to accommodate for a loss of power cable-out. The condition of the standby batteries 70 will determine if an affected area experiences a cable-out as a result of the power loss. If the batteries are at full power, then the batteries may be able to provide power during a power loss.
To test the status of such standby batteries 70, cable systems must periodically send a technician out to the battery sites to physically test each battery unit. Such a procedure of determining the status of the standby batteries 70 is very costly and time consuming.
Also, and with reference to FIG. 1 of the present specification, several amplifier stages 10(n) are formed along the cable transmission path to ensure that the transmission signal provided to the users 20 is at an appropriate level. These amplifiers may include manual trunk amplifiers, automatic trunk amplifiers, trunk/bridging amplifiers, line extending amplifiers, and may also include AC power supply units or power inserts. If one of these amplifiers 10 malfunctions, a cable-out may occur to a user. In such a situation, to determine the cause of the cable-out, the cable system will have to send a technician out to check all possible causes of the cable-out, and to determine whether the amplifier stages 10 have any malfunctions. Such a procedure of determining the status of the amplifiers 10 is very time consuming and costly to the cable system.
Another problem with cable systems is that cable systems are required by the Federal Communications Commission to test for signal leakage or radiation. Conventionally, this test is performed by sending a technician out into the cable franchise area with a detector for detecting for such signal leakage or radiation. Again, such a testing operation which requires a time consuming operation by a technician is very inefficient.
One common and significant inefficiency in the operation of a standard cable system such as is shown in FIG. 1 is the necessity for a manual contact or disconnect of the service at the tap 15(n). That is, in conventional cable systems, each time a user 20 requests a connect or disconnect, the cable system must dispatch a technician to the appropriate tap 15(n) to connect or disconnect the service. This is a costly and time consuming operation and a significant drawback in such a system.
There has also been an increase in the demand for two-way communication between a cable user and the cable control system. For example, such two-way communication can be used to allow the cable user 20 to order pay-per-view programming being offered by the cable system. An effective supply of such programming is important for a cable system as it is a significant source of revenue for the cable system. At the present time, systems for allowing the user to control such pay-per-view operations either require the user to have a specialized cable box and the cable system must be designed for two-way communication or the user must call the cable system to order special programming.
The two-way communication system requires very complicated circuitry in allowing two-way communication along the cable, and is particularly difficult to implement in cable systems which have already been installed and designed without such a feature. The user call system is cumbersome for the user and requires extensive communication equipment hooked to the phone lines.